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Solar energy harvesting in photoelectrochemical solar cells
Research publication
Abstract
Here we study different approaches for increasing energy harvesting in titania based photoelectrochemical solar (PES) cells. We study the light harvesting of PES cells when photonic crystal and photonic sponge architectures are used. We also report on the influence of the surface corrugation of the metal electrode on the harvesting of photocarriers in solar cells.
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Figures
Source: I. Rodriguez et al., J. Mater. Chem. 17, 3205-3209 (2007). Reproduced with permission from the Royal Society of Chemistry.
Source: I. Rodriguez et al., J. Mater. Chem. 17, 3205-3209 (2007). Reproduced with permission from the Royal Society of Chemistry.
Source: I. Rodriguez et al., J. Mater. Chem. 17, 3205-3209 (2007). Reproduced with permission from the Royal Society of Chemistry.
Source: I. Rodriguez et al., J. Mater. Chem. 17, 3205-3209 (2007). Reproduced with permission from the Royal Society of Chemistry.
Source: I. Rodriguez et al., J. Mater. Chem. 17, 3205-3209 (2007). Reproduced with permission from the Royal Society of Chemistry.
Source: I. Rodriguez et al., J. Mater. Chem. 17, 3205-3209 (2007). Reproduced with permission from the Royal Society of Chemistry.
Research fields
Bottom-up
Nanoparticulate TiO₂ is organised as inverse opals and hierarchical photonic sponges before being assembled into dye-sensitised photoelectrochemical cells. Reference electrodes with compact particle packing keep the semiconductor chemistry constant while changing the optical architecture.
Characterization
SEM, optical spectra and current–voltage curves compare pore hierarchy, light harvesting and photovoltaic output. The measurements show that the disordered sponge can outperform the periodic inverse opal because multiple scattering raises absorption without depending on a narrow photonic stop band.
RESEARCH TOPICS
HarvestingThe paper compares three routes to improve dye-sensitised TiO2 cells: an ordered inverse opal, a broadband photonic sponge and corrugation of the collecting metal electrode. Current–voltage curves and photocurrent spectra are measured under AM1.5 illumination at 1000 W m⁻². The inverse opal concentrates enhancement near a photonic-band feature, whereas the sponge scatters over a wider spectral range. Corrugating the electrode addresses a different bottleneck by increasing metal–semiconductor contact and shortening the path that photocarriers must travel before collection.
InterferenceThe ordered inverse opal uses Bragg interference and reduced group velocity near its photonic stop-band edge, so enhancement is spectrally selective. The quasi-Apollony sponge deliberately abandons a single lattice constant: interconnected voids from 150 to 1500 nm scatter many wavelengths and trap light over much of the visible range. Comparing their photocurrent spectra separates narrow-band photonic-crystal localisation from broadband multiple scattering. The article therefore tests two distinct optical mechanisms rather than treating every porous TiO2 electrode as the same “light-trapping” structure.
MaterialsThe ordered electrode is an approximately 8 μm TiO2 inverse opal, while the sponge is templated from a 23 μm random mixture of latex spheres with diameters 1500, 400, 300 and 150 nm in an 82:12:4:2 volume ratio. Reference electrodes are made with the same thickness and chemistry so topology, not composition, drives the comparison. Firing at 450 °C produces anatase and improves electrical connectivity between nanoparticles, a necessary step because better optical trapping is useful only if photogenerated charge can reach the contact.
ChemistryTitanium isopropoxide infiltrates the colloidal templates and is converted into nanoparticulate TiO2; subsequent removal of the polymer leaves either periodic or quasi-fractal macropores. The cells are dye-sensitised and use the same chemical preparation for structured and reference electrodes. This controlled chemistry exposes the effect of architecture, but it also reveals a constraint: processing conditions compatible with fragile templates can reduce the absolute photovoltaic performance, so optical enhancement and optimized electrochemistry must ultimately be developed together.